Apparatus for cutting screws or spirals.



No. 70|,225. I Patented May 27, I902.

- H. C. ROBINSON. I APPARATUS FOR CUTTING SCREWS 0R SPIBALS.

(Application filed May 17, 1901.) (No Model.) 4 ShaetsShael l.

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n1: Norms Parana co. Pnmouma, wasumomu, By a No. 701,225. Patented May27, I902. H. c. nosmsou.

APPARATUS CUTTING SCREWS 0B SPIRALS.

(Application filed May 17, 1901.) (No Model) I I 4 Sheets8heet 2.

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No. 701,225. Patented ma 27, I902. H. c. noamson. A APPARATUS FORCUTTING SCREWS 0B SPIRALS.

(Application filed May 17, 1901.)

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No. 70!,225. Patented May 27, I902.

H. C. ROBINSON.

APPARATUS FOR CUTTING SCREWS 0B SPIRALS.

(Application filed May 17, 1901. (No Model.) 4 Sheets-Sheet 4.

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from a lesser to a greater diameter.

UNTTnp STATES PATENT OFFICE.

HUGH CECIL ROBINSON, OF LONDON, ENGLAND.

APPARATUS FOR CUTTING SCREWS OR SPIRALS.

SPECIFICATION forming part of Letters Patent No. 701,225, dated May 27,1902.

Application filed May 17, 1901.

T0 and whom it may concern:

Be it known that I, HUGH CECIL RoBINsoN, a subject of the King of GreatBritain, residing at London, England, have invented certain new anduseful Improvements in Apparatus for Cutting Screws or Spirals, of whichthe following is a specification.

In cutting screws or spirals (hereinafter called spirals it is necessaryfor their perfect production that the tool, whether it be a revolvingcutter or an ordinary non-rotary tool, shall be placed at a'definiteangle in relation to the work, which angle is determined by the pitch ofthe spiral and the diameter of the material on which the spiral is to becut. There is one angle for each pitch and particular diameter at whichthe tool can work without cutting away or damaging the side of thespiral as the cutting proceeds.

In cutting spirals on plain cylinders the angle once determined is notaltered; but when the work varies in its diameter-t'. e., is notcylindrical-41w pitch or number of threads per unit length being,however, kept constant, it is necessary in order to cut the spiralcorrectly that the angular inclination of the tool shall vary with everyincrease or decrease of the diameter, so as to maintain the plane of thetool parallel to the tangent 'to the thread at the cutting-point.

My invention is designed to provide means whereby the angle of the tool,whether it be a revolving cutter or anordinary non-rotary cutting tool,is automatically varied with every alteration in the diameter of thework upon which the spiral is being cut, so as to maintain the correctangle for the tool, hav ing regard to such diameter at the point wherethe tool is cutting.

In turning objects of varying diameter or radius the cutter-frame ortool-holder is usually held in a transversely-movable carriage ortool-slide on the slide-rest, and it is clear that the said tool-slideand with it the tool must be made to approach more nearly to the axisabout which the work revolves when passing from a larger to a smallerdiameter and must recede from the axis when passing By my invention Itake advantage of this transverse movement of the tool-slide on theslide-rest Serial No. 60,771. (No model.)

for the purpose of obtaining the required variation of the angle of thetool.

According to my said invention the cutterframe or tool-holder isrotatably mounted on or in the said tool-slide or transversely-movablecarriage of the slide-rest and is connected through suitable belt orother gearing to a guide-frame with a slider, forming a lever, whichguide-frame is pivotally mounted on the said tool-slide. The slider isfurnished with a pivot-pin, which is connected to ad= justing mechanismmounted on the saddle of the slide-rest and which can be set at anydesired distance from the locus or path of the axis of oscillation ofthe said lever in the movement of the said tool-slide toward and awayfrom the Work. By these means as the tool-slide is moved in and out thesaid lever will be oscillated and the cutter-frame or toolholder willthereby be turned through a corresponding angle, the amount of suchrotation being dependent on the perpendicular distance of the saidpivot-pin 'from the locus or path of the axis of oscillation of the saidlever. I also provide means comprising a split collar withclamping-screw for locking the cutter-frame or tool-holder at anydesired angle, this being advantageous in cases where automaticadjustment of the angle of the cutter or tool is not required.

In the accompanying drawings I have shown how my said invention can beconveniently and advantageously carried into practice.

Figure 1 is a plan of my improved apparatus in which a rotary cutter isemployed. Fig. 2 is a sectional front elevation on the line C D, Fig. 1.Fig. 3 is a section on the line A B, Fig. 1. Fig. i is a section on theline E F, Fig. 3, drawn to a larger scale, illustrating a detail ofconstruction. Fig. 5 is a partial side elevation illustrating a modifiedform of transmission-gearing for connecting the cutter-frame and theoscillating lever on the tool-slide. Fig. 6 is a diagram illustratingthe operation of my improved device.

Like figures of reference indicate corresponding parts throughout thedrawings.

1 is the cutter-frame, rotatably mounted on one end of a bush or stem 2,secured in the transversely-movable tool-slide 3. The said frame carriesa cutter-spindle 4:, on which is mounted a rotary cutter 5, said spindlebeing driven by a band 6, passing over adjustable guide and tensionpulleys7 from a pulley 10 on the inner end of a shaft 8. This shaft isjournaled in the bush 2 and is provided at its outer end withcone-pulleys 9, whereby it can receive motion from any suitable drivingcord or belt. By this arrangement the angle of the cutter-spindle can bevaried without materially interfering with the tension of thedriving-band on the cone 9. The pulley 10 and the driving-band 6 mayinsome instances be substituted by bevel-gearin g.

Around the hub of the cutter-frame 1 are arranged a couple of bands orcords 11, whose ends are fixed to the hub. These bands pass around thehub in opposite directions and extend over guide -pulleys 12 to rings13, around which they pass in opposite directions and to which theirends are secured. The rings13 are mounted on a sleeve 14, which turns ona pin 15 on the transversely-movable slide 3, and the said rings areadjustable relatively to the sleeve 14 by means of teeth 16,formed'thereon and engaging with tangent screws 17, journaled' in ablock 18, secured to the said sleeve, so as to enable the bands 11 to bedrawn up taut and the frame 1 and sleeve 14 to be connected bytransmissiongearing which is free from lost motion.

The sleeve 14 is provided at the top with a double lever-arm in the formof a guide-frame 19, and in this frame there moves a slider 20, which isconnected by means of a'pivot-pin 21 to a block 22. This block isadapted to slide over the stem of a T-piece 23 and can be secured in anydesired position thereon by means of a set-screw 24. The cross-arms ofthe .T-piece are supported parallel to the axis of the lathe-mandrel andof the work in suitable sockets in two uprights 25, fixed on thelongitudinally-movable carriage or saddle 26 and are capable of beingsecured in any desiredposition by the set-screws 27. The said cross-armsof the T-piece may be graduated to facilitate the setting of the saidT-piece in any desired position.

The motions of the slides or carriages 3 and 26. are obtained, forexample, as follows: The saddle 26 is provided with a nut 28, engagingwith a leading-screw 29, which can be rotated'in any suitable knownmanner. The tool-slide 3 is provided with an arm 30, having anadjustable projection 31, adapted to engage with a templet 32, securedto a bracket carried by the frame of the slide-rest 33. The

, projection 31 is held in contact with the tom- Around the lower partof the sleeve 14 is arranged a split collar 38, which is anchored to theslide 3 and is provided with a clamping-screw 39, whereby it can becontracted so as to hold fast the sleeve 14, and therefore also theframe 1, against rotation when it is desired to use the tool at a fixedangle.

The setting of my improved apparatus is effected as follows: Theclamping-screws 27 and 24 having been loosened, the T-piece is adjustedin the sockets of the uprights 25, so as to make the distance betweenthe axes of the sleeve 14-2'. e., of the lever 19and of the pivot-pin 21when the lever 19 is parallel to the line joining the lathe-centersequal to the pitch of the spiral to be cut divided by 6.28318 (2a). Thissetting can be facilitated by having the T-piece graduated. Theset-screws 27 are then tightened up.

To ascertain the correct position for the pivot-pin 21, the cutting-toolor revolving cutter is turned to the correct angle to suit the angle ofthe spiral having regard to the diameter of the work at the particularpart where the cutter is at the moment situated. This movement will betransmitted through the cords 11, sleeve 14, guide frame or lever 19,slider 20, and pivot-pin 21 to the block 22,

thus bringing the said block 22 into the proper position, in which it isthen fixed by the clamping-screw 24, or the correct position of thepivot-pin 21 may be ascertained by arranging the lever 19 parallel tothe axis of the work and then moving the slide 3 inward un til the edgeof the cutter is in line with the lathe-centers. The screw 24 is thentightened and the apparatus is set. On drawing back the slide 3 fromthis position the arm 19 will be turned through an angle equal to thatthrough which the tool is required to turn to maintain its parallelismwith the inclination of the spiral, and While at work the 1 angle of thecutting-tool or revolving cutter will be automatically varied as thetool-slide is moved toward and away from the axis of the work in strictagreement with the variations in the angle of the spiral being cut. Theprinciple on which this adjustment is based may be illustrated withreference to Fig. 6, in which 45 is the work, 1' the radius of the workat the cutting-point, Zthe instantaneous value of the length (measuredon the periphcry) of one convolution of the thread corresponding to theradius rat the cutting-point,

and p the pitch expressed as the axial lengthv of one convolution of thethread, this last quantity being a constant for a given piece of work.Moreover, the angle which the guide frame or lever 19 makes with theline b I) joining the lathe-centers or with the lines 6 21 and 15 fparallel thereto is equal or proportional to the angle which the planeof the cutter 5 makes with the horizontal. It will be seen that when theradius of the work is zero these angles will be zero, and theinstantaneous length Z of one convolution of the thread will be equal top; but when the radius of the Work is r the cutter 5 and pivot-pin 15will t t+r so that in order to obtain the required automatic adjustmentof angle of the plane of the cutter the distance 6 21 of the axis of thepivot-pin 21 from the line 0 c or locus of the pivot-pin 15 must be inthe ratio of to the distance e 15 of the axis of the pivot-pin 15 fromthe foot of the perpendicular from 21 onto the line 0 c. From this itfollows that when the line a 15 is equal to r the line a 21 must beequal to 19 divided by 271.

In the modification shown in Fig. 5 the cords 11 are replaced by bands42 of steel or other suitable material, united by connecting-bands 43,which pass around guide-pulleys 44. This gear afiords great strength,while at the same time retaining the requisite flexibility, and issuitable for use on lathes for heavy Work.

What I claim is-- 1. The combination of a slide-rest, a cutter or toolframe and a lever both pivotally mounted on the transverse slide of saidslide-rest, gearing connecting said cutter or tool frame and said leverso that one cannot turn without the other, and means pivotally andadjustably connecting said lever to the longitudinal slide of theslide-rest, substantially as, and for the purpose, hereinbeforedescribed.

2. The combination, in a lathe, of a sliderest, a cutter or tool frameand a guide-frame with a slider forming a lever, both frames pivotallymounted on the transverse slide of said slide-rest, gearing connectingsaid cutter or tool frame and said guide-frame, an adjustable blockcarried by the longitudinal slide of said slide-rest, and a pivot-pinconnecting said slider and said adjustable block, substantially as, andfor the purpose, hereinbefore described.

3. The combination, in a lathe, of a sliderest, a cutter or tool frameand a guide-frame with a slider forming a lever both frames beingpivotally mounted on the transverse slide of said slide-rest, bandsconnected at their ends to said cutter or tool frame and said guideframerespectively,tan gent wheels and screws for adjusting said bands, apivot-pin on said slider, and means for connecting said pivotpin to thelongitudinal slide of the slide-rest, substantially as, and for thepurpose, hereinbefore described.

4:. The combination, in a lathe, of a sliderest, a cutter or tool frameanda guide-frame with a slider forming a lever both frames pivotallymounted on the transverse slide of said slide-rest, gearing connectingsaid cutter or tool frame and said lever, brackets mounted 011 thelongitudinal slide of said slide-rest, a T-piece having its cross-armsadj ustably secured in said brackets, a block adj ustably secured on thestem of said T-piece, and a pivotpin on the slider and working in saidblock, substantially as hereinbefore described.

5. The combination, in a lathe, of a sliderest, a bush or stem mountedin the transverse slide of said slide-rest, a cutter or tool holderrotatably mounted on the end of said bush or stem,a cutter-spindlepivotally mounted in said holder, a spindle journaled in said bush orstem, gearing connecting said cutterspindle and the spindle in saidbushor stem, gearing for driving the spindle in said bush or stem, aguide-frame pivotally mounted on said transverse slide, a slider in saidguideframe, gearing connecting said cutter or tool holder with saidguide-frame, and a pivot-pin on the slider adjustably connected to thelongitudinal slide of said slide-rest, substantially as, and for thepurpose, specified.

6. The combination, in a lathe, of a sliderest, a cutter or tool holderpivotally mounted on the transverse slide of said slide-rest, a hub onsaid holder, a sleeve pivotally mounted on said transverse slide, ringsrotatably mounted on said sleeve, teeth formed on said rings,tangent-screws journaled in a bracket on said sleeve, flexible bandseach connected at one end to one of said rings and at the other to thehub of said cutter or tool holder, a guide-frame mounted on said sleeve,a slider in said guideframe and a pivot-pin on said slider andadjustably secured to the longitudinal slide of said slide-restsubstantially as described.

7. The combination, in a lathe, of a sliderest, a cutter or tool frameand a guide-frame with a slider forming a lever, both frames pivotallymounted on the transverse slide of said slide-rest, a sleeve rigidlyattached to said guide frame, a split collar encircling said sleeve andanchored to said transverse slide, a clamping-screw uniting the ends ofsaid split collar, gearing connecting saidcutter or tool my hand inpresence of two subscribing witnesses.

HUGH CECIL ROBINSON. \Vitnesses:

W. M. HARRIS, WALTER J. SKERTEN.

